World Bulletin / News Desk
Children and teens who had higher levels of the chemical bisphenol A in their urine were more likely to be overweight or obese th an children with lower levels, U.S. researchers said on Tuesday.
The findings do not prove that BPA, a type of synthetic estrogen, causes children to gain weight. But researchers said hormone-like chemicals co uld be one reason for an increase in childhood obesity, besides diet and exercise.
"Children are uniquely vulnerable to environmental chemicals," said Dr. Leonardo Trasande of New York University School of Medicine, who worked on the study published in the Journal of the American Medical Association.
Trasande theorized that ingesting extra BPA could throw off young people's hormonal balance and disrupt their metabolism.
BPA has already been banned in the United States from baby bottles and sippy cups, but the U.S. Food and Drug Administration has not banned the chemical from aluminum cans and other types of packaging because it has not been definitively shown to cause harm to adults.
Other studies have suggested a link between BPA and higher weight in adults.
Trasande and colleagues analyzed data from a nationwide health and nutrition survey conducted between 2003 and 2008. Nearly 3,000 subjects ages 6 to 19 were weighed, measured and had their urine tested for BPA. They also answered a range of diet and lifestyle questions.
In total, about one-third of the children were overweight and 18 percent were obese.
The researchers found that slightly more than 10 percent of children with the lowest BPA levels were obese, compared to 22 percent of those with the highest BPA levels.
That was after taking into account how much the children ate, their age, race and gender.
Trasande said he was struck by the strength of that link, but it does not mean extra BPA in children's diets was responsible for the extra pounds they were carrying.
There are a couple of other theories, Trasande said.
"Obese children could ingest food that has higher BPA content - it could be what we call reverse causation," he said. Or, they could have higher BPA stored up in their bodies and release more BPA.
"Those are both very plausible explanations," he said.
Of course, an unhealthy diet and poor physical activity "are still the biggest causes of childhood obesity," Trasande said.
Karin Michels, an epidemiologist from the Harvard School of Public Health in Boston, agreed there is "accumulating evidence" that BPA may be linked to obesity and related diseases like diabetes - although most of that research was conducted on animals.
Her own study, which used similar health and nutrition data, found a link between BPA levels in urine and adult weight.
"We still don't really know how safe bisphenol A is," said Michels, who was not involved with Trasande's study.
While more research is underway, Michels said it makes sense to avoid polycarbonate bottles, aluminum cans and other products containing BPA if there are other options.
"I think we should be on the safe side," she said. But, "I don't think we have to panic about it at this point."